How many days until you can tell if a chicken egg is going to hatch?

It's impossible to tell exactly when a chicken egg will hatch, even if you know the incubation period. Here's why:

* Incubation period varies: The average incubation period for chicken eggs is 21 days, but it can range from 19 to 23 days depending on the breed, temperature, and humidity.

* Individual variation: Even within the same clutch of eggs, individual chicks can hatch a day or two earlier or later.

* Candling: While candling (shining a light through the egg) can help you determine if the egg is fertile, it's not a precise indicator of hatch date. Candling can help you identify developing chicks, but not predict the exact day of hatching.

What you can do:

* Keep a close eye: Once the incubation period is nearing its end, you can start checking the eggs more frequently for signs of hatching, like pip (a small crack in the shell) and movement.

* Provide a good environment: Make sure the incubator is maintained at the correct temperature and humidity to give the chicks the best chance of hatching successfully.

Instead of trying to pinpoint the exact hatch date, focus on providing the best possible conditions for the developing chicks.